SINKHOLE OPENING AND CLOSING APPARATUS OPERATABLE IN BACKWARD FLOW

A device for opening and closing a drain operated by a backward flow is provided to cut off a drain at ordinary times and to open a drain when draining off rainwater or domestic wastewater, or when flowing backward. A device for opening and closing a drain operated by a backward flow comprises a housing and a plate unit, wherein the housing is inserted to a drain and provided with a hanging projection(101) to make the housing put on the drain and to support a drain cover(200), a backing plate(103) to limit the downward rotation of a first plate, a support plate(105), and stopping pins(107,109) to limit the upward rotation of a first plate and a second plate, and the plate unit is installed to the inside of the housing to make opening and closing movements and composed of a first plate(111) and a second plate(113) to cut off the inside of the housing fully, and auxiliary plates(115) to fill up the space between the two facing second plates and the space between the second plate and the housing, to absorb shock, to prevent abrasion and to smooth a rotational movement.